Gretchen Schaefer
202.833.7311
CSPA FACT SHEET ON ANTIMICROBIAL WIPES
A study released in early June has confirmed the effectiveness of United Kingdom disinfectant wipes as compared to a natural antimicrobial (grapefruit extract) wipe and a non-antimicrobial detergent wipe. The study was conducted by the School of Pharmacy, Cardiff University, in Wales. In addition to demonstrating many of the strengths of disinfectant wipe products, the study also highlighted the ongoing concern of cross contamination between surfaces while cleaning. This is of heightened importance in hospitals where improper cleaning could spread rather than prevent hospital acquired infections like methicillin-resistant staphylococcus aureus (MRSA).
In the Cardiff study, surfaces were intentionally contaminated with high levels of S. aureus and S. aureus MRSA, well beyond the levels found on environmental surfaces in real hospital settings. The study design measured the ability of disinfectant, natural antimicrobial and detergent wipes to kill, remove, and transfer bacteria after a short 10 second exposure. Unlike a real use setting, the residual disinfectant on the test surface was neutralized after the 10 second exposure to stop the continued antibacterial action of the disinfectant wipe. In the U.S., approved contact times for hospital disinfectant wipes range from 30 seconds – 10 minutes. U.S. disinfectant labels inform the user to clean the surface if heavy soil is visible such as the heavy bacterial deposit used in this study, and to thoroughly wet the surface such that it remains wet for the labeled contact time. Thus, the Cardiff study evaluated the wipe products under worst case conditions and did not use the disinfectant wipe in a manner that would follow typical U.S. Environmental Protection Agency registered use directions.
Wipes are a unique combination of chemistry and substrate science. Wipes offer many benefits to users including no diluting, ready-to-use, easy treatment of contoured or complex surfaces, eliminates reuse of mops or rags, eliminates contamination of a mop/rag bucket, and frequent discard as the liquid is imparted to the surface which is more likely to assist in interrupting the transfer of organisms between surfaces.
The U.S. EPA requires that wipes undergo simulated use testing in the AOAC Germicidal Spray Test which similar to the Cardiff study evaluates products under a worst case bioload. The AOAC study requires that a laboratory technician wipe at least ten sequential surfaces to show a wipe’s ability to kill all the organisms dried on each surface as well as demonstrate that the wipe is able to kill any organisms that may be transferred between surfaces. The test surfaces are typically loaded with 6 logs or 1,000,000 dried bacteria /surface. The U.S. regulations require that no survivors remain on 59 of 60 surfaces per each of three lots of product; therefore, a U.S. registered product will have demonstrated the ability to kill high numbers of dried bacteria on the initial surface treated as well as 9 subsequent surfaces.
The Cardiff researchers did not identify whether any of the wipes tested were registered for use in the U.K. Registration and efficacy testing regulations in the U.K. are quite different from those required by the U.S. EPA. In the United States, wipes that bear disinfectant claims must be tested, registered, and labeled according to the regulations and policies of the U.S. EPA.
Although the Cardiff study employed very challenging study conditions, the following important conclusions were made by the study authors:
- Disinfectant wipes achieved a significant reduction in MRSA on surfaces in the presence and absence of organic load as compared to detergent and natural antimicrobial wipe formulations.
- "Natural antimicrobial wipes and detergent wipes have little and no antimicrobial action against S. aureus." This confirms previous publications that have shown that commercial antimicrobial products are as much as 100 times more effective than homemade mixtures at killing harmful disease-causing microorganisms.
- "The survival of bacteria on natural antimicrobial wipes and detergent wipes leads to repeated microbial transfer." This reinforces the importance of choosing a disinfectant wipe over a natural or detergent wipe to reduce bacteria.
- Disinfectant wipes transferred fewer bacteria to subsequent surfaces than the natural and detergent wipes. This also points out the importance of choosing a disinfectant wipe over a natural or detergent wipe to reduce bacteria.
Though the bacterial transfer portion of the study has gotten significant attention, the results mirror other published work on the application of disinfectants through mops or rags (J. Hosp. Infect. 2004; 56:S70-S75; Applied Micro 1971; 693-697). Yet other published literature has shown that mops retain high numbers 3-5 log or 1,000-100,000 bacteria/gram (J Food Prot. 2007;12:2878-83). Ready- to- use, disposable disinfectant wipes offer a valuable, microbiologically sound adjunct to traditional reusable applicators. In a subsequent interview of the author, they confirm this and share that a subsequent study that will be released later showed that a wipe outperformed a disinfectant sprayed on a rag (Infection Control Today, September 2008). Dr. Jean-Yves Maillard emphasized, “So, it seems that impregnated wipes, if used appropriately, might contribute better to decreasing microbial bioburden from surfaces.”
Although Dr. Maillard suggests that each wipe should be used on a single discrete surface, US labeling more importantly emphasizes thoroughly wetting the surface(s) and observing the contact time posted on the label to achieve the full disinfection which is supported by the simulated use testing required for U.S. registration.
As demonstrated in the Cardiff study, it is critical to select a U.S. EPA registered disinfectant wipe and to follow the label directions to effectively kill, remove, and avoid the transfer of bacteria. In addition the study validates that natural antimicrobial wipes and detergent wipes do not provide the same level of antimicrobial protection as disinfectant wipes.
